Control for rheostats



April 2o, 1954 G. J. MUCHER CONTROL FOR RHEOSTATS Filed April 16, 1951 ATTORNEYS Patented Apr. 20, 1954 CGNTROL FOR RHEOSTATS George J. Mucher, Rochester, N. H., assignor to Clarostat Mfg. Co., Ine., Dover, N. H., a corporation of New York Application April 16, 1951, Serial No. 221,276

This invention relates to a structurally and functionally improved control of the electric type and especially aims to provide a unit the parts of which may be readily adjusted.

It is an object of the invention to provide a control such as a potentiometer and which may be used either singly or in a gang assembly with a number of similar or-identical units; the present invention serving to permit of a ready phasing of the several elements so that their electrical characteristics and operating cycles may coincide.

n further object is that of providing a potentiometer or similar structure in which a definite voltage ratio or resistance value will be set up when a predetermined angular relationship of the contact arm of the unit is established with respect to a demte stop of the rotor or radial point.

An additional object is that of furnishing a structure which will embody a relatively simple design involvingr few parts capable of quantity production and ready assemblage to furnish a compact and simple mechanism operating for long periods of time with freedom from all dimculties.

With these and other objects in mind, reference is had to the attached sheet of drawings illustrating practical embodiments of the invention and in which:

Fig. l is a side elevation of an assembly of units;

Fig. 2 is a face view of one of such units with the cover removed and showing a structure embodying the present teachings;

Fig. 3 is a transverse sectional view taken along the lines 3 3 and in the direction of the arrows as indicated in Fig. 2;

Fig. 4 is a face view of the rotor in enlarged scale;

Fig. 5 is a fragmentary sectional view taken along the lines 5-5 and in the direction of the arrows as shown in Fig. 4; and

Fig. 5 is a fragmentary sectional view of a part of the assembly as shown in the preceding views.

Referring primarily to Fig. 1 there have been shown three units arranged in gang assembly relationship. This is merely illustrative; potentiometers andk similar units in the case of servo mechanisms involving in most instances a considerable number of assemblies. As is well understood, such a grouping includes in each unit a resistance which is traversed by an element of a rotor. A shaft common to the servo units extends through them. Terminals extend from each unit and are connected in desired electrical circuits.. It isA essentialthat. the rotors Voffeach.

14 Claims. (Cl. 201--48) unit occupy positions upon the shaft such that identical electrical values or characteristics are present on the part of each unit or else that these values have a definite and predetermined rela tionship. To assure this result it has been customary to furnish a coupling (either embodying a set screw or functionally similar element) by means of which the position of the rotor can be adjusted with respect to the shaft. As is also well understood, the tolerance permitted in this connection is very small and an operator has had to work with painstaking care to relate each of the units of a gang assembly to the other and then secure the parts against subsequent disarrangement.

The reference numerals I0, H and I2 designate the casings of controls. These casings are preferably formed of (ii-electric material and are identical. Bridging portions I3 and recesses iii are formed in opposed edges of the units. These serve to lock the casings with respect to each other and prevent their relative movements when a number of them are assembled. A shaft if: common to all of the units may extend through the same. As in Figs. 2 and 3 terminals such as IG, il and i8 conveniently project from the peripheral edges of the casings and are connected by leads i@ to, for example, the ends of a resistance element En and a contact ring 2l. The resistance as shown will ordinarily be arranged in the form of a circle or arc and may be wire wound. It is obvious that other forms of resistance element might be employed.

In any event the surface of the resistance element is traversed by a contact arm which forms a part of a rotor assembly. Collector ring 2| is also traversed by a wiper arm and electrically connected to the Contact arm which traverses the resistance. Conveniently both of these arms are carried by a hub which by means of a set screw is secured against movement with respect to the rotating shaft. t is by means of this structure that the rotor may be positioned with respect to the operating shaft and then may be locked against movement with respect to that shaft. it is in connection with this technique of positioning and locking that dimculties have heretofore been experienced.

With especial reference to Fig. 3 a single shaft has been indicated at 22 which shaft extends rotatably through the base of the housing 23 and is encircled by a hub 2li. This hub carries set screw 2-5 engageable with the surface of the shaft to lock. the hub in position. A dielectric plate 26 is affixed tohub 24. The former mounts the arm traversing collector resistance 20 as well as the arm traversing ring 2|. These arms in accordance with conventional practice are electrically connected and may include any desired number of parts.

According to the present teachings and as shown especially in Figs'. 2, 4 and 5, a spring wiper arm 21 traverses collector ring 2-I. This arm extends upwardly and is connected by a stud 28 to the outer face of plate 26. A second arm 29 overlies that portion of arm 2'! which is disposed upon plate 26 and a common, pivoty 30. passes through the forward ends of both arms 29 and.2'l. In this manner arm 2lv is secured against rotation with respect to hubfZfi. and plate 26. However, arm 29 may pivot and is formed with an opening 3l through whichstudpasses. The area of this opening is substantially greater than the diameter of stud 28. The latter has aixed to it within the space donned by the edges of the opening a cani 32. The diameter of that cam is substantially equal to the space between the side edges or opening 3l. The stud terminates in a manipulatingA portion such as a head 33. Conveniently that head is non-circular so that its edges may be engaged by a suitable wrench. Otherwise, it may be formed in any desired manner so asto be capable of being rotated with respect tothe plate or contact carrier 26.

So rotated, it is apparent that contact arm 29 will be swung with, respect to its pivot 3e. Accordingly, the outer end of the arm which traverses the resistance will have imparted to it a movement tangential to the surface of that resistance. Therefore, according to one extreme of adjustment oi the cam 32 the arm may be advanced a matter of, for example, two or three degrees for the position` which it assumes when the cam is in its other extreme of adjustment. Adjusted throughl this range, the arm will include or exclude a portion of the resistance strip. In the instance of a wire wound unit, several strands will be involved. Thusfby the adjustment, resistance will be added or subtracted to a desired point of. adjustment usually in relation to other` units on thesaine shaft. Accordingly, it is apparent that an operator may secure the rotor assembly in approximately correct position with respect to the shaft 22. This securing will be eiiected by set screw 2&5 or its equivalent. With the parts so secured, and by rotating the stud and cam 32 a Vernier adjustment is obtained without difficulty. At this. time it isl to be understood that while in certain respects it is preferred to have the contact arms respectively traversing the resistance strip and contact ring, generally embody an assembly such as has been shown, they might be entirely separate units. Also, any desired number of parts might provide these units.

Regardless of detailed structures such as this, it will be understood that an` operator may with minimum skill and expenditure of time assemble a unit so that its rotor will occupy substantially apredeterinined position with respect to a given stop or electrical value. With the parts locked he may then precisely adjust them toestablish deiiniteelectric values. Asl aforo brought out, this will be especially desirable in cases of gang assemblies involving a number of potentiometers or similar units. It will permit of a ready phasing of these units` to establishpredetermined resistance andvoltage ratios. When thev Dsitia1ii-ris` of, the parts is completely cor,.-

- tion a. plurality of units each including a circularresistance, a` mounting therefor, a rotor encircled by said resistance and a contact arm cooperative with said resistance and movably connected to said rotor to be shirtable in an arcuate direction with respect thereto, a shaft common to all ofl said units, means for rotatably supporting said shaft, 1neans for securing the several rotors ci' said units against movement with respeci. to said shaft whereby when the latter is rotated, each of said contact arms will traverse the resistance with which it cooperates and adjust-ing means indivi-dually connected to each of rotors and arms for moving the latter in arcuate path with respect to the former and with a stationary condition ofsaid shaft advancing and retracting a given arm with reference to the resistance withwhich it cooperates,

A control assemblylcomprising in combination, a plurality` ofv units each including a circular resistance, aY mounting therefonarotor encircled by-said resistance anda contact arm cooperative Withsaid resistance and movably connected to said rotor to be shiitable in an arcuate direction with respect thereto, ashait common to allot' said units, means for rotatably supporting said shaft, means for securing the several rotors of said units against movement with respect to said` shaft whereby` when the latter is rotated, each ofrsaid contactarms will traverse the resistance with which it cooperates, adjustingmeansfindividually connected toieach 0f said rotors and arms for moving the latter in an arcuate path with respect to the former and with a stationary condition of said shaft advancing andretracting a given armwith r `ference to the resistance with which it cooperates and means connecting theseveral mountings for the resistances to prevent movements of the same with respect to each other..

3, A controlassembly comprising in combination a plurality of units each including a circular: resistance, a mounting,r therefor, a rotor encircled by said resistance and a contact arm cooperative with said resistance and movably connected to said'rotor to be shiftablein an, arcuate direction with respect, thereto,` a shaft common to,v all.v of said units, each of said rotors being shiftablev around said shaft to correspondingly shift the armcarriedthereby with respect to the resistance with which it cooperates, means for locking -eachoisaid rotors/against shifting with respect to said shaft whereby when` the latter is rotated: each of said contactarme will traverse the resistance with which it cooperates and adjusting means individually. connected to each of said rotors and arms for shifting the latter in an arcuate path with respect to the former and withy a stationary condition of said shaft advancing andretracting said arms with respect to Athe resistancesawithl,whichthey cooperate.

4. A control including in combination an arcuately disposed resistance, means for mounting the same, a hub encircled by said resistance, a contact arm movable with respect to said hub and traversing Said resistance as said hub is rotated, means carried by said hub and cooperative with said arm for advancing and retraeting the latter with respect to said resistance while said hub remains stationary and means for rotating said hub.

5. A control including in combination an arcuately disposed resistance, means for mounting the same, a hub encircled by said resistance, a Contact arm movable with respect to said hub and traversing said resistance as said hub is rotated, means carried by said hub and cooperative with said arm for advancing and retracting the latter with respect to said resistance While said hub remains stationary, means whereby said hub and arm may be locked against relative movements and means rotating said hub.

6. A contro-i including in combination an arcuately disposed resistance, means for mounting the same, a hub encircled by said resistance, a contact arm movable with respect to said hub and traversing said resistance as said hub is rotated, means carried by said and cooperative with said arm for advancing and retracting the latter with respect to said resistance while said hub remains stationary, a shaft rotatable with respect to said hub and means for rocking said hub against movement with respect to said shaft.

7. In a control a hub to be supported for rotau tion, a resistance-traversing movably connected to said hub and means carried by said hub and cooperative with said arm for shifting a portion of the latter under a stationary condition of said hub in a direction around the axis oi said hub.

8. In a control a hub to be supported for rotation, a resistance-traversing arm movably connected to said hub, means carried by said hub and cooperative with said arm for shifting a portion of the latter, under a stationary condition of said hub, in an arcuate direction around the axis of said hub and means whereby said arm and hub may be locked against relative shifting.

9. In a control a hub to be supported Jfor rotation, a resistance-traversing arm movably connected to said hub, means carried by said hub and cooperative with said arm for shifting a portion P of the latter, under a stationary condition of said hub, in an arcuate direction around the axis of said hub and a Wiper arm also connected to said hub and secured against shifting With respect to the same.

10. In a control in combination a hub to be supported for rotation, an arm having an outer contact portion, said arm being of lengthwise curved configuration and means for pivotally securing the opposite arm ends to said hub with the body of said arm arcuately circling the hub center and its contact end extending beyond said hub to provide a resistance-engaging contact end which is adjustable over said resistance as said arm is swung around its pivot.

11. In a control in combination a hub to be supported for rotation, an arm having an outer contact portion, said arm being of lengthwise curved conguration, means for pivotaliy securing the opposite arm end to said hub with the body of said arm arcuately circling the hub center and its Contact end extending beyond said hub to provide a resistance-engaging contact end which is adjustable over said resistance as said arm is swung around its pivot and means for locking said arm in the position to which it has been adjusted.

12. In a control in combination a hub to be supported for rotation, an arm having an outer contact portion, said arm being of lengthwise curved configuration, ri-,cans for pivotally securing the opposite arm end to said hub with the body of said arm arcuately circling the hub center and its contact end extending beyond said hub to provide a resistance-engaging contact end which is adjustable over said resistance as said arm is swung around its pivot and means carried by said hub and cooperating with said arm for swinging the latter around its pivot.

13. In a. control to form a part of an electrical resistance unit a mounting to be coupled against movement with respect to a rotary operating member, a contact arm rockingly mounted by said member and having an outer end to traverse a circular path as said mountingis rotated and in such traversal to cooperate with the resistance and whereby, with said mounting stationary, said arm may be moved with respect to said mounting to advance and retract the outer end of said arm with respect to a resistance.

le. In a control to form a part of an electrical resistance unit a mounting to be coupled against movement with respect to a rotary operating member, a contact arm movably mounted by said member and having an outer end to traverse a circular path as said mounting is rotated and in such traversal to cooperate with the resistance whereby, with said mounting stationary, said arm may be moved with respect to said mounting to advance and retract the outer end of said arm with respect to a resistance, said arm presenting an edge portion and a rotary cam mounted by said mounting and cooperating with said edge portion to move said arm.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,613,606 Flarnmer Jan. 11, 1927 1,735,268 Ellis Nov. 12, 1929 2,059,712 Schellenger II Nov. 3, 1936 2,176,090 McAllister et al Oct. 17, 1939 2,473,409 Beechlyn June 14, 1949 

